Combined linear and circular drive mechanism

Abstract

A combined linear and circular drive mechanism for driving a spindle in an up or down direction and also in a circular path about an axis parallel to the spindle. The mechanism has a dual or compound nut which is driven to rotate in a fixed plane so as to drive a spindle threaded therethrough in an up or down direction. The dual nut mechanism has a pair of nut components having respective eccentrically positioned threaded openings, the openings being displaced from each other such that one of the nut components engages the threaded spindle to drive it in a first direction while it is being carried in a circle, and a second nut component engages the spindle to drive it in the reverse direction, also while the shaft is being rotated in a circle. The threaded portion of the spindle is bounded by unthreaded portions, such that when it is driven to an upper or lower limit by one of the nut components such nut component ceases to engage the spindle threading, whereupon when the nut drive is reversed the other nut component engages the threaded portion and drives the spindle in the other direction.

I claim: 
     
       1. A drive mechanism for driving a spindle, said spindle having a threaded portion of a predetermined diameter and unthreaded portions bounding each side of said threaded portion, said mechanism comprising: (a) A generally cylindrical spindle carrier, having a longitudinal opening through which said spindle extends, said opening being eccentrically positioned in said carrier;   (b) A cylindrical bushing having a bushing opening, said spindle carrier being positioned concentrically within said bushing opening, and bearing means for movably bearing said spindle carrier within said bushing;   (c) Nut means for engaging said threaded portion of said spindle, said nut means having two nut components, each component having an internally threaded longitudinal opening, said spindle extending through each of said nut openings, said nut components being integrally fixed to and carried in said bushing opening, said nut component openings having a greater diameter than said spindle diameter and having respective different center axes such that when said spindle threaded portion engages the internal threaded opening of one of said nut components it is free of the internal opening of the other nut component; and   (d) Whereby rotation of said bushing in a clockwise direction causes one of said nut components to drive said spindle in a first longitudinal direction and rotation in a counter clockwise direction causes the other of said nut components to drive said spindle in the reverse longitudinal direction, and said spindle is moved in a circular path about the center axis of said bushing while said bushing is rotated.   
     
     
       2. The drive mechanism as described in claim 1, wherein said nut component center axes are displaced relative to each other such when a first of said nut components is aligned with one of said unthreaded portions the other of said nut components is in position to engage said spindle threaded portion. 
     
     
       3. The drive mechanism as described in claim 2, comprising means for maintaining said nut components contiguous to each other. 
     
     
       4. The drive mechanism as described in claim 2, comprising means for maintaining said nut components displaced longitudinally from each other. 
     
     
       5. The drive mechanism as described in claim 3, comprising a fixed housing, and bearing means for supporting rotation of said bushing within said fixed housing. 
     
     
       6. The drive mechanism as described in claim 1, comprising a pipette carried by the bottom portion of said spindle. 
     
     
       7. An assembly comprising a longitudinally extending element and drive means for controllably driving said element in opposite longitudinal directions and for driving said element in a circular path about a longitudinal axis parallel to and offset from said longitudinal directions, characterized in that, said element has a threaded portion and unthreaded portions at the boundaries of said threaded portion; and   said drive means comprises a cylindrical bushing having a center longitudinal axis along said longitudinal axis, nut means connected to and positioned within said bushing for engaging said threaded portion of said element, said nut means having two abutting nut sections each with an internally threaded hole, each of said nut holes being positioned at a respective different eccentric position relative to said bushing center axis, said spindle extending through said nut section holes, whereby when said bushing is rotated in a first direction, a first of said nut sections engages and drives said element in a first of said opposite longitudinal directions and when said bushing is rotated in a second opposite direction the second of said nut sections engages and drives said element in the opposite of said longitudinal directions, and when either of said nut portions is engaged with said element and drives said element in a given direction, one of said unthreaded portions limits the extent of longitudinal drive in said given direction.   
     
     
       8. An assembly for driving a threaded spindle or the like, said spindle having a threaded portion bounded by unthreaded portions, comprising first and second nut elements having threads complimentary to that of said threaded spindle, means for driving said spindle in a circular path about a longitudinal axis, and means for alternately engaging said spindle with said first nut element and for driving said spindle in a first longitudinal direction parallel to and offset from said axis, and for engaging said spindle or the like with said second nut element and driving said spindle in an opposite longitudinal direction parallel to and offset from said axis, whereby when one of said unthreaded portions reaches the one of said nut elements driving said spindle, said spindle is continuously driven in said circular path and is not driven in a longitudinal direction.